Tertiary alkyl ethers, like methyl t-butyl ether (MTBE) and ethyl t-butyl ether (ETBE), are extremely useful as octane enhancers and fuel oxygenates in gasoline. These ethers are conveniently prepared by the acid-catalyzed electrophilic addition of primary alcohols to iso-butene. Commercially, certain strong-acid, cation-exchange resins prepared by sulfonating macroporous monovinyl aromatic monomer/divinylbenzene copolymers provide ideal physical and catalytic properties for such etherification reactions; see, for example, W. Neier in "Ion Exchangers," Konrad Dorfner, Ed., Walter de Gruyter, Berlin-New York, 1991, pp. 1002-1009. Strong-acid, cation-exchange resins specifically developed and sold for catalytic applications in t-alkyl ether manufacture, e.g., Rohm & Haas' Amberlyst.TM. A-15 and A-35 resins, Dow's Dowex.TM. M-3I resin and Purolite's CT-175 resin, are all derived from macroporous styrene/divinylbenzene copolymers having at least about 20 weight percent divinylbenzene crosslinker. Resins made from lower levels of crosslinker generally exhibit inferior catalytic activity.
U.S. Pat. No. 5,244,926 discloses the advantages of performing suspension polymerizations for producing monovinyl aromatic monomer/divinylbenzene copolymers under high temperature conditions attained adiabatically, i.e., under conditions in which a high temperature, about 120.degree. C. or higher, of the reactor contents is reached by not removing the heat in the reactor that is generated by the polymerization reaction. These advantages include better reactor utilization, shorter reaction times and increased product throughput. The patent only teaches that these copolymers and resulting ion-exchange resins are useful to separate chemical species from solutions and to prepare polymeric adsorbents.
However, when suspension polymerizations using the recipes developed for commercial resins/copolymers are run at high temperatures, i.e. about 120.degree. C. or higher reached adiabatically or otherwise, and the resins are subsequently sulfonated to prepare strong-acid, cation-exchange resins for use as etherification catalysts, the catalytic activity of the resulting resins is adversely affected, i.e., the rate of conversion of alcohol and olefin to ether is reduced. Another disadvantage associated with conventional processes is the high cost of the divinylbenzene crosslinker used therein. Thus, it would be very advantageous if a new process were available that could take full advantage of the benefits associated with a high temperature polymerization process without reducing the catalytic activity of the subsequently sulfonated monovinyl aromatic monomer/divinylbenzene copolymer products. In addition, it would be very commercially attractive if the new process to make the copolymer required less of a very expensive material, such as divinylbenzene crosslinker.